In fascinating detail, Amato explores how the concept of twos—contrasts, comparisons, polarities, dualities and contradictions—has been fundamental to human thought from infant development to national identities. In Amato’s telling, two becomes, literally, who we are. His wide-ranging mind ranges across history, religion, art, philosophy, war, politics, and language. The book devotes significant space to essential figures who’ve considered those topics at length: Montaigne, William James and Isaiah Berlin. Here, too, are Aristotle, Augustine, Aquinas, Descartes, Dostoevsky, and Freud.